Usual dose: To treat mild to moderate depression, clinical trials have used 900 to 1,200 milligrams per day. To treat anxiety, a dose of 600 milligrams per day was used.

Are there any risks? St. John's wort can interfere with many drugs and should not be used during chemotherapy. In some people, St. John's wort can cause a skin rash after exposure to sunlight. Other possible side effects include insomnia, vivid dreams, restlessness, anxiety, agitation, irritability, stomach upset, diarrhea, fatigue, dry mouth, and dizziness.

What does the research say? St. John's wort has been shown to be as effective as some drugs in relieving mild to moderate depression. Results of its effectiveness in controlling anxiety are mixed.